So, why are there still fish?
America was settled by people from England. Why are there still Englishmen?
Why do people always ask this? Do you really think that it is a problem for the theory of evolution that bacteria/apes/fish/whatever still exist and that somehow all of the scientists just completely overlooked this problem and when you point it out we will all throw up our hands and say, "Oh no! How foolish we have been!"?
As the other poster pointed out, if America was settled by Englishmen, why are there still Englishmen today?? And once you are born, how can your parents possibly have any other children? They way some people speak about this you'd think people would be required to keel over dead after producing their first baby (which would soon make us extinct, alas).